title: "Fast proteins" with a unique essential amino acid content as an optimal nutrition in the elderly: growing evidence.
abstract: OBJECTIVE
  Adequate protein intake is crucial to maintain body protein content in elderly subjects, but quality of dietary proteins should be also considered since amino acid composition and rate of protein digestion modulate amino acid availability. This study investigates whether the efficacy of optimal protein intake levels for protein retention in the elderly is influenced by protein quality.
  
  
  METHODS
  We investigated the effect of a 10-day adequate-protein (AP) or high-protein (HP) diet together with the protein source as caseins (CAS) or soluble milk proteins (PRO) on whole-body (WB) protein synthesis (PS) and protein breakdown (PB) in 4 groups of healthy elderly men (mean ± SEM: 71.8 ± 24.4 yr). The study consisted of two periods of 4 h each: a post-absorptive period and a postprandial period. The fed state was defined by consumption every 20 min and for 4 h, of either 15 g or 30 g of PRO or CAS. Steady-state WB and splanchnic leucine kinetics were measured using a continuous infusion of L-[1-13C]leucine in the postabsorptive state and L-[1-13C]leucine infusion plus oral L-[5,5,5-2H3]leucine in the postprandial state.
  
  
  RESULTS
  WB PS was stimulated by feeding only with HP diets, whereas WB PB corrected for splanchnic extraction showed a similar pattern of post-feeding decrease in all groups. Consequently, net leucine balance was greater in the postprandial state after HP meals than after AP meals, with PRO meals leading to a better postprandial leucine balance (3.63 ± 0.16 μmol kg FFM(-1) min(-1)vs. 2.77 ± 0.21 μmol kg FFM(-1) min(-1) for PRO HP and CAS HP, respectively; P = 0.005).
  
  
  CONCLUSIONS
  Postprandial protein retention was better improved in elderly men by an increase in protein intake when the protein supplementation was provided as fast-digesting proteins that induce high leucine availability.
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Gryson
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Walrand
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Giraudet
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Paulette
authors.initials: P
authors.lastname: Rousset
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Migné
authors.affiliation: Lactalis, Lactalis R&D, Retiers F-35000, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Bonhomme
authors.affiliation: Lactalis, Lactalis R&D, Retiers F-35000, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Le Ruyet
authors.affiliation: INRA, UMR1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France; CHU Clermont-Ferrand, Clinical Nutrition Department, Clermont-Ferrand F-63003, France. Electronic address: Yves.Boirie@clermont.inra.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Boirie
mesh_terms: D000368:Aged; D000601:Amino Acids, Essential / Q000008:administration & dosage* / Q000097:blood; D015992:Body Mass Index; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage; D003611:Dairy Products / Q000032:analysis; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage / Q000493:pharmacokinetics; D008297:Male; D062407:Meals; D008894:Milk Proteins / Q000008:administration & dosage; D009752:Nutritional Status; D019518:Postprandial Period
chemical_list: D000601:Amino Acids, Essential; D002364:Caseins; D004044:Dietary Proteins; D007328:Insulin; D008894:Milk Proteins; D007930:Leucine
keywords: Elderly; Leucine; Nutrition; Protein anabolism; Sarcopenia; Soluble milk proteins